A photographic plate-making process comprises a process to convert a document with a continuous tone to a dot image. In this process, an infectious development technology has been used as a photographic technology to reproduce images with a super high contrast.
A lithographic type silver halide photographic light-sensitive material used for infectious development comprises of a silver bromochloride emulsion wherein an average grain size is 0.2 .mu.m, for example, and grain distribution is narrow, a grain has a regular shape, and a silver chloride content is high (50 mol % or more). By processing this lithographic silver halide photographic light-sensitive material with an alkaline hydroquinone developing solution having a low sulfite ion concentration, so-called a lithographic developing solution, an image with a high contrast, a high sharpness and a high resolution can be obtained.
However, since the above lithographic developing solution is liable to be air-oxidized, preservability thereof is not sufficient. Accordingly, it is difficult to keep the quality of development constant in continuous running.
On the other hand, methods to obtain an image with high contrast without using the above lithographic developing solution are known. For example, Japanese Patent Publication Open to Public Inspection No. 106244/1981 (hereinafter referred to as Japanese Patent O.P.I. Publication) discloses a method to incorporate a hydrazine derivative in a silver halide photographic light-sensitive material and to process the light-sensitive material with an alkaline developing solution containing an amino compound. This and other methods make it possible to obtain high contrasted image even when the light-sensitive material is processed with a developing solution having high preservability and capable of processing rapidly. In addition, a method to incorporate a redox compound in a light-sensitive material for improving the quality of dot is disclosed in Japanese Patent O.P.I. Publication No. 285340/1990. In addition, a light-sensitive material having a layer containing a redox compound and a light-sensitive emulsion layer containing a hydrazine derivative for widening dot gradation is disclosed in Japanese Patent O.P.I. Publication No. 174143/1991.
In the above methods, a light-sensitive material had to be processed with a developing solution with pH of more than 11.2 in order to bring out the high contrast property of the hydrazine derivative sufficiently. In a developing solution having a high pH of 11.2 or more, a developing agent is easily oxidized when allowed to stand in contact with air. Though it is more stable than the lithographic developing solution, it is often impossible to obtain an image with high contrast due to the oxidation of the developing agent.
In order to overcome this shortcoming, Japanese Patent O.P.I. Publication No. 29751/1988 and European Patent Nos. 333,435 and 345,025 disclose silver halide photographic light-sensitive materials containing a contrast increasing agent which increases the contrast of light-sensitive material even with a developing solution with comparatively low pH. When using the above methods, stability against air oxidation of a developing solution is noticeably improved compared to the lithographic developing solution. However, it is necessary to add sulfite of 0.25 mol per 1 l to the developing solution for further stabilization.
On the other hand, a black-and-white photographic light-sensitive material for plate-making use is, in most cases, processed by the use of an automatic processing machine after exposure. In addition, it is also ordinary that the above light-sensitive material is processed so that stable photographic performance can be obtained while replenishing a certain amount of developing solution in proportion to the area of the light-sensitive material. Conventionally, in order to obtain above high contrast image, a light-sensitive material has been processed while replenishing a developing solution replenisher in an amount of 300 ml or more per 1 m.sup.2 of the light-sensitive material in order to prevent reduction in the ability of a developing solution caused by fatigue or air oxidation of the developing solution in continuous processing.
However, being influenced by recent increased concern about environment, reduction of the amount of the effluent of developing solution has become urgent necessity. When a high contrast light-sensitive material is processed with a developing solution with high sulfite salt concentration in an automatic processing machine under a condition of a small amount of developing solution replenisher of 200 ml or less per 1 m.sup.2 of the light-sensitive material, a problem of silver stein, so-called silver sludge, is easily caused. In the case of silver sludge, silver dissolves out of the light-sensitive material and gets into the developing solution and is precipitated on various parts of the automatic processing machine such as rollers and gears to be black or silver-sticking substances so that the surface of the light-sensitive material is contaminated and scratched, deteriorating finished performance. Accordingly, it is important to reduce silver sludge for photographic processing of a high contrast light-sensitive material for plate-making use.
In addition, when the light-sensitive material is processed by an automatic processing machine, the total processing time (dry to dry) from the moment when the leading edge of a film is inserted in the automatic processing machine up to the moment when the trailing edge comes out of the drying zone has hitherto been 90 seconds or more. However, due to the increase of the number of prints and shortening of labor hours, reduction of photographic processing time is demanded. Accordingly, when a high contrast light-sensitive material containing a hydrazine derivative is subjected to rapid processing wherein the total processing time (dry to dry) is less than 60 seconds and subjected to continuous processing in an automatic processing machine under the above-mentioned conditions, silver sludge is easily worsened, photographic processing becomes unstable and sand-like fogging occurring at an unexposed portion after being processed, so-called black spots, which is specific to a light-sensitive material containing the hydrazine derivative easily occurs.
As an silver-sludge-agent ordinarily added to a developing solution, it is conventional to add 2-mercapto-1,3,4-thiazoles (British Patent No. 940,169), 2-mercapto-1,3,4-thiazoles, 1-phenyl-5-mercapto tetrazoles (U.S. Pat. No. 3,173,789), 2-mercaptobenzoxazole and 2-mercaptobenzoimidazole (Photogr. Sci. Eng., 20, 220 (1976)). However, in the case that a hydrazine derivative is added to a light-sensitive material and it is processed with an alkaline developing solution wherein an amino compound is contained, when the above-mentioned anti-silver-sludge agent is used, the effect of preventing sliver sludge was insufficient. In addition, sensitivity reduction and contrast lowering were caused and the effect of preventing black spots was insufficient.